A substantial angle of oscillation of an axle, such as the front axle of a tractor, is usually desirable to provide good vehicle stability on rough ground. When the terrain is quite irregular oscillation of such tractor axle allows the tractor wheels to remain infirm contact with the ground to give the tractor good support.
It is necessary, of course, to limit the angle of axle oscillation such that the tractor tires do not contact portions of the tractor body. Tractors, therefore, have axle stops on their axle housings, and abutment members (sometimes called "bolsters") in fixed position above their axles to be engaged by the axle stops as the axle pivots well away from its normal horizontal orientation.
While a substantial angle of axle oscillation is desirable for stability, in some cases it is desirable to restrict the maximum angle of oscillation. For any given set of tractor wheels and tires, a further restriction in the maximum angle of axle oscillation increases the maximum turning angle which is achievable before the tractor tires hit the body of the tractor. That is, limiting the angle of axle oscillation shortens the turning radius of the tractor, making it more maneuverable.
Tractor maneuverability is very important in a number of tractor uses. For example, feed lot work requires substantial maneuverability in a situation in which instability due to uneven ground is rarely a problem. Therefore, restriction of the angle of axle oscillation is highly desirable.
In some cases the use of large front wheels and tires on a tractor is desirable. For example, when a tractor has a mechanical front-wheel drive larger wheels and tires are highly desirable. When the axle pivots, larger tires tend to hit the tractor body more easily, that is, during smaller turns. Therefore, greater restriction of the angle of maximum axle oscillation tends to allow the use of tractor tires which are either greater in diameter or wider in tread width, or both.
Given the number of tasks for which tractors are used, it is sometimes desirable to change the maximum angle of axle oscillation to adapt the tractor to the immediate task. In some cases this means increasing the maximum angle of axle oscillation and in other cases it means decreasing such maximum angle.
Various devices have been used in the past to limit and in some cases change the angle of axle oscillation. The prior art includes limiting means of various kinds, including those disclosed in the following patents: U.S. Pat. Nos. 1,765,764 (Jett); 4,500,113 (Law); 3,805,908 (Thompson); and 2,560,144 (Vorhees). The prior art also includes the use of crude devices, such as bolts holding a series of washers, to further restrict the angle of axle oscillation.
While various axle oscillations stop means have been disclosed in the prior art, there is a need for an accessible, easily installable and easily adjustable device for further limiting the maximum angle of axle oscillation in tractors.